1. Field of the Invention
The present invention relates to a manufacturing technique for an integrated circuit device, and more particularly, to a contact plug and a method for manufacturing the same.
2. Description of the Related Art
Trench metal-oxide semiconductor field effect transistors (MOSFETs) are common semiconductor power devices which can withstand high voltage and exhibit low turn-on resistance and high turn-on current. In contrast to planer semiconductor power devices, trench MOSFETs need to form one or more contact plugs in a silicon substrate so as to electrically connect to exterior components. A method for manufacturing the contact plug includes depositing a titanium layer and a titanium nitride layer in an opening so as to prevent conductive materials in the opening from diffusing outward and to provide the conductive materials in the opening with improved adhesion. Next, a rapid thermal process (RTP) is performed such that the titanium layer reacts with the silicon substrate to form a titanium silicide layer, thereby reducing the contact resistance of the contact plug. Next, a conductive layer is deposited to fill in the opening, and the manufacturing process is complete.
In such a method for manufacturing the contact plug, however, during the RTP, the titanium nitride layer is jostled by the titanium layer thereunder due to the different formation rates of the titanium silicide layer at the sidewall and bottom of the opening. Hence, the titanium nitride layer at the bottom corner of the opening may be torn apart and experience cracking. The conductive materials in the opening may thus diffuse outward via the cracks, resulting in leakage paths of the transistors and thereby increasing leakage current. Moreover, if the method utilizes gases containing fluorine (for example, WF6), fluorine ions may also pass through the cracks and react with the silicon substrate, thereby resulting in Si loss near the bottom corner of the contact plug.
Therefore, a novel contact plug and a method for manufacturing the same are desired to solve or mitigate the aforementioned problems.